Plasticity and Learning Flashcards
What is postnatal growth of the brain guided by?
learning
What is the critical period for visual cortex development in cats, monkeys, and humans?
- cat: 2 weeks - 3 months
- monkey: 2 months - 12 months
- human: 6 months - 3 years
What is neuronal plasticity in the mammalian visual system driven by?
neuronal activity
Eye closure for a couple days during ________________________ induces movement of __________________________________. This does not occur after ______________.
the critical period; spines as part of synaptic plasticity; the critical period
What regulates the critical period?
cortical GABA inhibition
TRUE or FALSE: inhibiting GABA signalling widens the critical period and increases plasticity
FALSE: enhancing GABA
What eliminates the critical period?
GABA neuron knockout (GAD2)
What are the 4 methods of critical period termination?
- myelination, and associated Nogo, which occurs at the end of the critical period; Nogo inhibits neuronal growth
- Development of adult perineuronal net (PNN), a web of CSPGs that wrap inhibitory neurons (GABA)
- reduction in growth potential of adult neurons, compared to neonatal neurons
- reductions in growth factors like BDNF and neuromodulators like NA (which modulate LTP)
What is the function of PNN?
limit plasticity with maturation
What are sone ways in which the PNN limit plasticity?
- physical barrier
- inhibitory molecules
- prevent lateral mobility of receptors
Missed skill development in critical periods leads to
____________________________.
smaller associated cortical areas
What is the order of critical periods for the following: sensory, language, other cognitive and motor functions
- sensory
- language
- other cog and motor function
Children without social interaction in critical period have _____________________.
less related frontal cortex
What are some ways via which critical-period plasticity may be restored in adults to treat SCI?
- blocking myelin inhibition of axon growth (eliminate Nogo)
- degrading PNN with chondroitinase (ChABC)
- transplant immature GABA neurons in visual cortex
- increase neuromodulators via antidepressants
- training or enriched environment to increase BDNF (use it or lose it)
- microglia-neuronal communication increases GABA neuron plasticity
What does ChABC digest?
CSPG and PNN
Transplanting inhibitory GABAergic neurons creates _______________________ in mice.
a new critical period
What does enriched environment lead to, in terms of plasticity?
- increases cortical thickness
- increases size of neurons
- increases number of spines/synapses
- increaes BDNF
Which reflex can be readily studied in humans to examine plasticity and learning? Why?
- monosynaptic stretch reflex
- resists external disturbances
Why do we need to regulate the stretch reflex?
because it can get in the way of voluntary movement
______________ inhibition turns off antagonist motor neurons when making movement. This is _____________ inhibition.
reciprocal; postsynaptic
TRUE or FALSE: Nodal Facilitation (GABAB) turns off reflex pathways when not needed and Presynaptic inhibition (GABAA) turns on sensory transmission to the brain.
FALSE:
- presynaptic inhibition (GABAB) = turn OFF reflex when not needed
- nodal facilitation (GABAA) = turn ON sensory transmission to brain
TRUE Or FALSE: GABAA modulates afferents to the brain, whereas GABAB increases synaptic inhibition
TRUE
Where are GABAA and GABAB receptors found on an axon?
- GABAA at nodes
- GABAB at terminals
Describe Nashner’s 1979 experiment. What was the main conclusion?
- ankle extensor stretch reflexes REDUCE body sway if foot is displaced horizontally, so the CNS AUGMENTS them in successive trials
- the same reflexes INCREASE body sway in a toe-up rotation about the ankle joint, so the CNS ATTENUATES them in successive trials
- main conclusion: context-dependence and adaptation may be controlled by cerebellum and reticular formation (i.e. good control can take over the reflex that makes you fall over)
Delays in the stretch reflex can cause ___________________________.
instability and tremor
TRUE or FALSE: experienced athletes and dancers have an enhanced stretch reflex
FALSE: they lack the stretch reflex
Why do experienced dancers and athletes lack the stretch reflex?
it can get in the way of their movements; i.e. the body has adapted inhibition of the stretch reflex and tremor
What happens to muscle oscillation if the stretch reflex is too late?
oscillations become bigger if the stretch reflex is activated at the wrong time, leading to tremor
With spinal cord injury, nerve injury, stroke or CP, the reflex pathways are disrupted, leading to __________________.
spasticity
With spinal cord injury, what does reduced reciprocal inhibition lead to?
co-contraction of muscles, leading to stiffness
With spinal cord injury, what does reduced preynaptic inhibition (via GABAB) lead to?
exaggerated reflexes
With spinal cord injury, what does sensory terminal sprouting and microglia plasticity lead to?
increased reflexes, which lead to spasticity and clonus
With spinal cord injury, what does increased nodal facilitation lead to?
unwanted reflex response in inappropriate muscles
What factors in spinal cord injury lead to spasticity or clonus?
- reduced reciprocal inhibition
- reduced presynaptic inhibition
- sensory terminal sprouting and microglia plasticity
- increased nodal facilitation
In motor neurons, what leads to sustained muscle spasms?
increase Na+ and Ca2+ currents
_____________ innervation of the spinal cord is lost, but _____________ receptors on motorneurons become constitutively active, further augmenting spasms.
serotonin, 5HT
What is used to treat spasticity?
- GABA agonists
- 5-HT antagonists
- botox
- surgery
- rehab
What happens to brain mapping when the 3rd digit of your hand is removed? What is this change guided by?
- 2nd and 4th finger mapping takes over
- guided by microglia
Sensation in phantom limb is evoked from stimulation of the _________ after 4 weeks after arm amputation and cortical remapping in adults.
face
